Method and apparatus for communicating in an increased coverage area to a wireless communication unit

ABSTRACT

A method for increasing coverage in a wireless communication system is described. The method comprises, at the network element: transmitting a first portion of subframes comprising a number of resource blocks to a first wireless communication unit in a first mode of operation, wherein the number of resource blocks are transmitted at a first power level per resource block; and transmitting, a second portion of subframes to a second wireless communication unit in a second mode of operation at a second power level, wherein the second portion of subframes comprise a lower number of resource blocks than the first portion of subframes and the lower number of resource blocks is transmitted at a second power level per resource block that is higher than the first power level per resource block.

FIELD OF THE INVENTION Related Application(s)

The field of this invention relates to a method and apparatus forproviding increased coverage to a wireless communication unit, such asuser equipment (UE), for example in a long term evolution wirelesscommunication system.

BACKGROUND OF THE INVENTION

A recent development of third generation (3G) wireless communications isthe long term evolution (LTE) cellular communication standard, sometimesreferred to as a 4^(th) generation (4G) system. 4G systems will bedeployed in existing spectral allocations owned by network operators andnew spectral allocations that are yet to be licensed. LTE devices areable to operate on carriers of bandwidth up to 20 MHz. FIG. 1illustrates a simplified block diagram of a downlink sub-frame of acarrier 100 comprising a legacy control channel region 105 and aplurality of resource blocks (RBs) 110 as stipulated in the LTEstandard. In FIG. 1, the RBs span a bandwidth of 20 MHz 115, where eachRB comprises twelve sub carriers and each sub carrier has a bandwidth of15 KHz. RBs comprise physical downlink shared channels (PDSCH).

The requirement to support a bandwidth of up to 20 MHz increases devicecost in comparison to lower bandwidth systems, such as the GeneralPacket Radio Service (GPRS). The cost of supporting high bandwidthdevices has led to an increasing desire to support low bandwidth (andhence low cost) LTE devices within higher bandwidth carriers. Examplesof devices that could beneficially use LTE include so-called machinetype communication (MTC) devices, which are typified by semi-autonomousor autonomous wireless communication devices communicating small amountsof data on a relatively infrequent basis. Examples of MTC devicesinclude so-called smart meters, which, for example, may be located in acustomer's house and periodically transmit information back to a centralMTC server data relating to the customer's consumption of a utility suchas gas, water, electricity and so on.

Whilst it can be convenient for a terminal such as an MTC type terminalto take advantage of the wide coverage area provided by a third orfourth generation mobile telecommunication network, there are at presentdisadvantages. Unlike a conventional third or fourth generation mobileterminal such as a smartphone, an MTC-type terminal is preferablyrelatively simple and inexpensive. The type of functions performed bythe MTC-type terminal (e.g. collecting and reporting back data to thenetwork) do not require particularly complex processing to be performed.In many scenarios, providing low capability terminals with aconventional high-performance LTE receiver unit capable of receiving andprocessing data from an LTE downlink frame across the full carrierbandwidth can be overly complex and expensive for a device which onlyneeds to communicate small amounts of data.

Some MTC devices (and in particular smart meters) may be installed inlocations where coverage is poor. For example smart meters may bedeployed in basements or cellars where there is significant penetrationloss through the building. In order to support communications to/fromthese MTC devices, a larger system gain (also referred to as maximumcoupling loss) needs to be supported by the wireless communicationsystem. Some known potential methods of increasing the supported systemgain include:

-   -   increasing the eNodeB transmit power. This requires the        installation of higher power (and more expensive) power        amplifiers at the eNodeB. There may be significant opposition to        the installation of such equipment by local residents.    -   use of external antennas at the UE. These external antennas may        be installed at street level and connected to the smart meter in        the basement. However, use of such external equipment is likely        to increase the cost of deployment by increasing installation        cost.    -   installation of extra network nodes, such as relays or femto        cells, adding cost and complexity to the wireless system.    -   significantly increasing the error correction coding (e.g.        repetition coding) applied to the signal. There would also be a        significant increase in the number of reference symbols applied.    -   application of beamforming or beam steering techniques; hence        concentrating the eNodeB energy at the UE. Such techniques might        require the addition of significant extra equipment at the        eNodeB.

SUMMARY OF THE INVENTION

The present invention provides communications units, integratedcircuits, methods for increasing communication coverage for wirelesscommunications units and tangible computer program products therefor, asdescribed in the accompanying claims. Specific embodiments of theinvention are set forth in the dependent claims. These and other aspectsof the invention will be apparent from and elucidated with reference tothe embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified diagram of a sub-frame transmitted by aneNodeB in a long term evolution (LTE) system.

FIG. 2 illustrates a 3GPP™ long term evolution (LTE) cellularcommunication system adapted in accordance with some example embodimentsof the present invention.

FIG. 3 illustrates an example block diagram of a wireless communicationunit, such as a 3GPP™ LTE user equipment adapted in accordance with someexample embodiments of the present invention.

FIG. 4 illustrates a simplified example schematic diagram of a modifiedsignal sent from an eNodeB.

FIG. 5 illustrates a simplified example schematic diagram of a packetdata control channel (PDCCH) that occupies subframes 1 and 2 allocatinga PDSCH occupying subframes 3 and 4.

FIG. 6 illustrates a simplified example flow diagram of eNodeB operationutilising aspects of the present invention.

FIG. 7 illustrates a simplified example flow diagram of UE operationutilising aspects of the present invention.

FIG. 8 illustrates a simplified example block diagram of referencesignal positioning within a legacy resource block and a fractionalresource block, according to aspects of the invention.

FIG. 9 illustrates a simplified example block diagram of a frequencyhopping technique, according to aspects of the invention.

FIG. 10 illustrates a simplified example block diagram of a transmissionof uplink signals on a single subcarrier.

DETAILED DESCRIPTION

Examples of the invention provide communication units, associatedintegrated circuits and methods for increasing system gain to provideenhanced coverage for devices. Although examples of the invention aredescribed with reference to improving the coverage area for a low costMachine-Type communication (MTC) device, relative to normal long termevolution LTE devices, it is envisaged that the inventive concept isalso applicable to other wireless communication devices, such as publicsafety devices.

In the context of the present invention, the term resource block isintended to encompass a set of time and/or frequency and/or coderesources. For example, in general in LTE downlink, a ‘resource block’would be considered to mean 12 subcarriers and 14 OFDM symbols. Askilled artisan will appreciate that the term resource block would meanother communication resources in other systems.

In particular, a method for increasing coverage in a wirelesscommunication system is described. The method comprises, at the networkelement: transmitting a first portion of subframes comprising a numberof resource blocks to a first wireless communication unit in a firstmode of operation, wherein the number of resource blocks are transmittedat a first power level per resource block; and transmitting, a secondportion of subframes to a second wireless communication unit in a secondmode of operation at a second power level, wherein the second portion ofsubframes comprise a lower number of resource blocks than the firstportion of subframes and the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block.

In this manner, when the eNodeB wishes to communicate to UEs in verypoor coverage situations, it is able to narrow the bandwidth of itstransmissions and transmit all available power in that narrowerbandwidth, for example, the eNodeB transmits a reduced number ofsubcarriers in the cell. The total power applied in the cell is,however, maintained. By operating in this mode, the power spectraldensity of the subcarriers that are transmitted is maintained, but thepower level per resource block is increased. Hence, the coverage area ofcommunications to/from the UE is increased and the power that the UEreceives per subcarrier is now greater. The noise power per subcarrierremains the same. Hence the signal power to noise ratio per subcarrierhas increased.

In some examples, the method may further comprise: scheduling a firstcontrol channel region in the first portion of subframes and schedulinga second additional separate control channel region in the secondportion of subframes, for example where the second portion of subframesmay comprise at least one from a group comprising: almost blanksubframes, multimedia broadcast single frequency network (MBSFN)subframes. In this manner, almost blank subframes and/or MBSFN subframesmay be used to implement a second additional control channel region forcommunicating with the wireless communication unit

In some examples, the method may further comprise scheduling the secondseparate control channel region in the second portion of subframesacross multiple subframes, for example where the second separate controlchannel region may comprise a control channel signal that allocates a(subsequent) shared downlink resource to the second wirelesscommunication unit

In some examples, at least one of the control channel signal and theshared downlink resource may be interleaved over a plurality of secondportion of subframes. In some examples, the lower number of resourceblocks used in the second portion of subframes may comprise less than asingle physical resource block. In this manner, a yet further increasein coverage range may be achieved and a sufficiently large number ofbits may be transmitted in a PDCCH or PDSCH compared to the case wheretransmissions are constrained to a single subframe.

In some examples, scheduling the second portion of subframes in timemultiplexed frequency hopped transmissions may be performed such thatmultiple wireless communication units are supported within availabledownlink resource in a first communication cell, for example byinserting a time gap between frequency hops, for example wherein aresource block in the frequency hopping comprises a first number ofsymbols and a second number of subcarriers. In this manner, frequencyhopping may be employed in order to address a potential increase ininterference into neighbour cells on those subcarriers that aretransmitted at higher power, by randomizing the interference across thesubcarriers in the neighbour cell. For example, if the neighbour celltransmits using the scheme disclosed herein, then an orthogonal hoppingsequence may be employed such that the transmissions in the two cellswill not collide.

In some examples, the method may further comprise determining a powerrequirement of multiple wireless communication units and scheduling anumber of resource blocks for the second subframes based at least on adetermined power requirement of the second wireless communication unit,for example by:

requesting a path loss measurement from the second wirelesscommunication unit,

receiving channel quality information transmitted by the second wirelesscommunication unit, or

receiving an indication from the second wireless communication unit ofthe power that it is using for its transmissions

In some examples, scheduling a second separate control channel region inthe second portion of a subframe may comprise scheduling at least oneof: a Physical Downlink Control Channel (PDCCH), a Physical Hybrid ARQIndicator Channel (PHICH) and a Physical Control Format IndicatorChannel (PCFICH), for example where the channels transmitted by thesecond additional separate control channel region occupy more than asingle subframe.

In some examples, the method may be employed in a long term evolutionwireless communication system.

Examples of the invention further provide a tangible computer programproduct comprising executable code stored therein for increasingcoverage in a wireless communication system, wherein the code isoperable for, when executed at a network element, performing theaforementioned method.

Examples of the invention further provide a network element forincreasing coverage in a wireless communication system. The networkelement comprises a transceiver operably coupled to a control processor,wherein the control processor is arranged to: transmit, a first portionof subframes comprising a number of resource blocks to a first wirelesscommunication unit in a first mode of operation, wherein the number ofresource blocks are transmitted at a first power level per resourceblock; and transmit, a second portion of subframes to a second wirelesscommunication unit in a second mode of operation at a second powerlevel, wherein the second portion of subframes comprise a lower numberof resource blocks than the first portion of subframes and the lowernumber of resource blocks is transmitted at a second power level perresource block that is higher than the first power level per resourceblock.

Examples of the invention further provide an integrated circuit for anetwork element for increasing coverage in a wireless communicationsystem. The integrated circuit comprises a control processor, arrangedto: transmit a first portion of subframes comprising a number ofresource blocks to a first wireless communication unit in a first modeof operation, wherein the number of resource blocks are transmitted at afirst power level per resource block; and transmit, a second portion ofsubframes to a second wireless communication unit in a second mode ofoperation at a second power level, wherein the second portion ofsubframes comprise a lower number of resource blocks than the firstportion of subframes and the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block.

Examples of the invention further provide a method for communicating inan increased coverage area in a wireless communication system. Themethod comprises, at a wireless communication unit: receiving in asecond extended coverage mode of operation, a signal comprisingsubcarriers transmitted at a second power level, wherein the signalcomprises a second portion of subframes, wherein the second portion ofsubframes comprise a lower number of resource blocks than a firstportion of subframes transmitted at a first power level in a firstnon-extended coverage mode of operation, and wherein the lower number ofresource blocks is transmitted at a second power level per resourceblock that is higher than the first power level per resource block.

Examples of the invention further provide a tangible computer programproduct comprising executable code stored therein for communicating inan increased coverage area in a wireless communication system, whereinthe code is operable for, when executed at a wireless communicationunit, performing the aforementioned method.

Examples of the invention further provide a wireless communication unitcomprising: a receiver for receiving in a second extended coverage modeof operation, a signal comprising subcarriers transmitted at a secondpower level, wherein the signal comprises a second portion of subframes,and a control processor, operably coupled to the receiver and arrangedto decode the signal, wherein the second portion of subframes comprise alower number of resource blocks than a first portion of subframestransmitted at a first power level in a first non-extended coverage modeof operation, and wherein the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block.

Examples of the invention further provide an integrated circuit for awireless communication unit comprising: a control processor arranged todecode a signal received in a second extended coverage mode ofoperation, wherein the signal comprised subcarriers transmitted at asecond power level and comprises a second portion of subframes, whereinthe second portion of subframes comprise a lower number of resourceblocks than a first portion of subframes transmitted at a first powerlevel in a first non-extended coverage mode of operation, and whereinthe lower number of resource blocks is transmitted at a second powerlevel per resource block that is higher than the first power level perresource block.

Referring now to FIG. 2, a wireless communication system 200 is shown inoutline, in accordance with one example embodiment of the invention. Inthis example embodiment, the wireless communication system 200 iscompliant with, and contains network elements capable of operating over,a universal mobile telecommunication system (UMTS™) air-interface. Inparticular, the embodiment relates to a system's architecture for anEvolved-UMTS Terrestrial Radio Access Network (E-UTRAN) wirelesscommunication system, which is currently under discussion in the thirdGeneration Partnership Project (3GPP™) specification for long termevolution (LTE), based around OFDMA (Orthogonal Frequency DivisionMultiple Access) in the downlink (DL) and SC-FDMA (Single CarrierFrequency Division Multiple Access) in the uplink (UL), as described inthe 3GPP™ TS 36.xxx series of specifications. Within LTE, both timedivision duplex (TDD) and frequency division duplex (FDD) modes aredefined.

The wireless communication system 200 architecture consists of radioaccess network (RAN) and core network (CN) elements 204, with the corenetwork elements 204 being coupled to external networks 202 (namedPacket Data Networks (PDNs)), such as the Internet or a corporatenetwork. The CN elements 204 comprise a packet data network gateway(P-GW) 207. In order to serve up local content, the P-GW may be coupledto a content provider 209. The P-GW 207 may be further coupled to apolicy control and rules function entity (PCRF) 297 and a Gateway 206.

The PCRF 297 is operable to control policy control decision making, aswell as for controlling the flow-based charging functionalities in apolicy control enforcement function PCEF (not shown) that may reside inthe P-GW 207. The PCRF 297 may further provide a quality of service(QoS) authorisation class identifier and bit rate information thatdictates how a certain data flow will be treated in the PCEF, andensures that this is in accordance with a UE's 225 subscription profile.

In example embodiments, the Gateway 206 may be a Serving Gateway (S-GW).The Gateway 206 is coupled to a mobility management entity MME 208 viaan S11 interface. The MME 208 is operable to manage session control ofGateway bearers and is operably coupled to a home subscriber service(HSS) database 230 that is arranged to store subscriber communicationunit 225 (user equipment (UE)) related information. As illustrated, theMME 208 also has a direct connection to each eNodeB 210, via an S1-MMEinterface.

The HSS database 230 may store UE subscription data such as QoS profilesand any access restrictions for roaming. The HSS database 230 may alsostore information relating to the P-GW 207 to which a UE 225 canconnect. For example, this data may be in the form of an access pointname (APN) or a packet data network (PDN) address. In addition, the HSSdatabase 230 may hold dynamic information relating to the identity ofthe MME 208 to which a UE 225 is currently connected or registered.

The MME 208 may be further operable to control protocols running betweenthe user equipment (UE) 225 and the CN elements 204, which are commonlyknown as Non-Access Stratum (NAS) protocols. The MME 208 may support atleast the following functions that can be classified as functionsrelating to bearer management (which may include the establishment,maintenance and release of bearers), functions relating to connectionmanagement (which may include the establishment of the connection andsecurity between the network and the UE 225) and functions relating tointer-working with other networks (which may include the handover ofvoice calls to legacy networks). The Gateway 206 predominantly acts as amobility anchor point and is capable of providing internet protocol (IP)multicast distribution of user plane data to eNodeBs 210. The Gateway206 may receive content via the P-GW 207 from one or more contentproviders 209 or via the external PDN 202. The MME 208 may be furthercoupled to an evolved serving mobile location center (E-SMLC) 298 and agateway mobile location center (GMLC) 299.

The E-SMLC 298 is operable to manage the overall coordination andscheduling of resources required to find the location of the UE that isattached to the RAN, in this example embodiment the E-UTRAN. The GMLC299 contains functionalities required to support location services(LCS). After performing an authorisation, it sends positioning requeststo the MME 208 and receives final location estimates.

The P-GW 207 is operable to determine IP address allocation for a UE225, as well as QoS enforcement and flow-based charging according torules received from the PCRF 297. The P-GW 207 is further operable tocontrol the filtering of downlink user IP packets into differentQoS-based bearers (not shown). The P-GW 207 may also serve as a mobilityanchor for inter-working with non-3GPP technologies such as CDMA2000 andWiMAX networks.

If the Gateway 206 comprises an S-GW, the eNodeBs 210 would be connectedto the S-GW 206 and the MME 208 directly. In this case, all UE packetswould be transferred through the S-GW 206, which may serve as a localmobility anchor for the data bearers when a UE 225 moves between eNodeBs210. The S-GW 206 is also capable of retaining information about thebearers when the UE 225 is in an idle state (known as EPS connectionmanagement IDLE), and temporarily buffers downlink data while the MME208 initiates paging of the UE 225 to re-establish the bearers. Inaddition, the S-GW 206 may perform some administrative functions in thevisited network, such as collecting information for charging (i.e. thevolume of data sent or received from the UE 225). The S-GW 206 mayfurther serve as a mobility anchor for inter-working with other 3GPP™technologies such as GPRS™ and UMTS™.

As illustrated, the CN 204 is operably connected to two eNodeBs 210,with their respective coverage zones or cells 285, 290 and a pluralityof UEs 225 receiving transmissions from the CN 204 via the eNodeBs 210.In accordance with example embodiments of the present invention, atleast one eNodeB 210 and at least one UE 225 (amongst other elements)have been adapted to support the concepts hereinafter described.

The main component of the RAN is an eNodeB (an evolved NodeB) 210, whichperforms many standard base station functions and is connected to the CN204 via an S1 interface and to the UEs 225 via a Uu interface. Awireless communication system will typically have a large number of suchinfrastructure elements where, for clarity purposes, only a limitednumber are shown in FIG. 2. The eNodeBs 210 control and manage the radioresource related functions for a plurality of wireless subscribercommunication units/terminals (or user equipment (UE) 225 in UMTS™nomenclature). Each of the UEs 225 comprise a transceiver unit 227operably coupled to signal processing logic 308 (with one UE illustratedin such detail for clarity purposes only). The system comprises manyother UEs 225 and eNodeBs 210, which for clarity purposes are not shown.As illustrated, each eNodeB 210 comprises one or more wirelesstransceiver (transmitter and/or receiver) unit(s) 294 that is/areoperably coupled to a control processor 296 and memory 292 for storing,inter alia, information relating to UEs and UE capabilities, for examplewhether the UE is capable of operating as a low bandwidth UE or whetherthe UE is able to operate in an extended coverage mode. Each eNodeB 210further comprises a scheduler 297, which may be operably coupled to theone or more wireless transceiver unit(s) 294, the control processor 296and memory 292. The base station (for example eNodeB 210) is arranged tosupport.

In example embodiments of the present invention, a control processor ofa network element, such as control processor 296 of eNodeB 210, isarranged to transmit a first portion of subframes comprising a number ofresource blocks to a first wireless communication unit, such as UE 225,in a first (non-extended coverage) mode of operation, wherein the numberof resource blocks are transmitted at a first power level per resourceblock. The control processor is further arranged to transmit a secondportion of subframes to a second wireless communication unit in a secondmode of operation at a second power level, wherein the second portion ofsubframes comprise a lower number of resource blocks than the firstportion of subframes and the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block.

In some examples, the control processor 296 may be located on anintegrated circuit (not shown).

Clearly, the various components within the eNodeB 210 can be realized indiscrete or integrated component form, with an ultimate structuretherefore being an application-specific or design selection. Further,although example embodiments of the invention have been described withreference to an evolved NodeB (eNodeB), it should be apparent to askilled person that example embodiments of the invention could beutilised with any network element, for example a NodeB within a 3GPP™high speed packet access (HSPA) network, or any other wireless networks.

Referring now to FIG. 3, a block diagram of a wireless communicationunit, adapted in accordance with some example embodiments of theinvention, is shown. In practice, purely for the purposes of explainingembodiments of the invention, the wireless communication unit isdescribed in terms of a wireless subscriber communication unit, such asa UE 225. The wireless communication unit 225 contains an antenna 302coupled to an antenna switch or duplexer 304 that provides isolationbetween receive and transmit chains within the wireless communicationunit 225. One or more receiver chains, as known in the art, includereceiver front-end circuitry 306 (effectively providing reception,filtering and intermediate or base-band frequency conversion). Thereceiver front-end circuitry 306 is coupled to a control processor 308(generally realized by a digital signal processor (DSP)). A skilledartisan will appreciate that the level of integration of receivercircuits or components may be, in some instances,implementation-dependent.

The controller 314 maintains overall operational control of the wirelesscommunication unit 225. The controller 314 is also coupled to thereceiver front-end circuitry 306 and the control processor 308. In someexamples, the controller 314 is also coupled to a buffer module 317 anda memory device 316 that selectively stores operating regimes, such asdecoding/encoding functions, synchronization patterns, code sequences,and the like. A timer 318 is operably coupled to the controller 314 tocontrol the timing of operations (transmission or reception oftime-dependent signals) within the wireless communication unit 225.

As regards the transmit chain, this essentially includes an input module320, coupled in series through transmitter/modulation circuitry 322 anda power amplifier 324 to the antenna 302, antenna array, or plurality ofantennas. The transmitter/modulation circuitry 322 and the poweramplifier 324 are operationally responsive to the controller 314.

In some examples, the control processor 308 may be located on anintegrated circuit (not shown). The control processor 308 in thetransmit chain may be implemented as distinct from the signal processorin the receive chain. Alternatively, a single processor may be used toimplement a processing of both transmit and receive signals, as shown inFIG. 3. Clearly, the various components within the wirelesscommunication unit 225 can be realized in discrete or integratedcomponent form, with an ultimate structure therefore being anapplication-specific or design selection.

In examples of the invention, the wireless communication unit 225comprises a receiver for receiving in a second extended coverage mode ofoperation, a signal comprising subcarriers transmitted at a second powerlevel, wherein the signal comprises a second portion of subframes. Thecontrol processor 308 is operably coupled to the receiver and arrangedto decode the signal, wherein the second portion of subframes comprise alower number of resource blocks than a first portion of subframestransmitted at a first power level in a first non-extended coverage modeof operation, and wherein the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block.

Referring now to FIG. 4 a schematic diagram illustrating an example of amodified LTE signal 400 as transmitted by the eNodeB, for example eNodeB210 of FIG. 2 (and received at the wireless communication unit, such asUE 225 of FIG. 2) is shown, comprising legacy control channel region 405and an additional control channel region 410 for coverage limited UEs,together with at least one resource block 415. In FIG. 4, the eNodeBtransmits only N_(coverage) resource blocks 420 in the carrier 425 (incomparison to the legacy case where the eNodeB would transmit using thefull N_(RB) resource blocks). For example, the transmissions to thecoverage limited UE (control and data) may cover N_(coverage)*12*15 kHz(where one resource block 415 covers 12 subcarriers and each subcarrierhas a bandwidth of 15 kHz). The number of resource blocks 415transmitted by the eNodeB would typically be an integer, in thisexample. However, in other examples, a non-integer value may be used,for example if N_(coverage)=0.5, the eNodeB will only transmit half aresource block, i.e. 6 subcarriers, in the bandwidth of the carrier 425.In this manner, the eNodeB is operable to vary the power spectraldensity of the transmitted N_(coverage) RBs 420, without increasing thetotal power applied to the carrier 425. In this example embodiment, theeNodeB is operable to dynamically determine how many resource blocks 420(N_(coverage)) to transmit. In this example, the control processor ofthe eNodeB may be arranged to determine the power requirements ofdifferent UEs in the system, and assign those UEs to subframes that aretransmitting at the appropriate transmit power per subcarrier and withthe appropriate number of subcarriers. In this example, the eNodeB maydetermine the number of resource blocks 420 to transmit (N_(coverage))by requesting a path loss measurement from a UE. In some examples, thismay be achieved via radio resource control signalling at connectionsetup.

In examples of the invention, the legacy control channel region 405 maybe arranged to carry PCFICH, PHICH and PDCCH. The separate controlchannel region 410 may be arranged to carry separate PCFICH, PHICH andPDCCH at a higher transmit power per subcarrier to coverage limited UEs.

In another example, the control processor of the eNodeB may be arrangedto determine N_(coverage) 420 by receiving channel quality feedbackindication(s) (CQI) from a desired UE. In this example, CQI feedbackindication(s) may be based on transmissions from the eNodeB in arestricted number of RBs 420. This is because it is possible, due to theincreased power spectral density of N_(coverage) RBs 420 transmitted inthis example embodiment, that a desired UE (if outside normal coveragearea) will not be able to receive transmissions at a legacy power persubcarrier from the eNodeB, and thus be unable to perform channelestimation, for the purposes of CQI determination, based on RBstransmitted at legacy power per subcarrier. In another exampleembodiment, CQI feedback may be based on a non-restricted number of RBs.

In another example embodiment, the scheduler 297 in eNodeB 210 may beoperable to schedule UEs in subframes according to their coveragerequirements. For example, UEs 225 that are determined to haverelatively poor channel conditions may be scheduled in subframes using asingle RB 415 at a high power level per subcarrier. Similarly, UEs 225determined to have relatively good channel conditions may be scheduledusing two RBs at a medium power level per subcarrier. In this manner,UEs 225 that are determined to have a certain channel condition may bedynamically scheduled to use anything from 0.5 to 100 RBs for a 20 MHzsystem, for example.

In this example embodiment, it is not necessary for the control channelregion 410 for coverage limited UEs to take up the same amount ofresource space (e.g. to occupy the same number of subcarriers) as thelegacy control channel region 405. However, in this example embodiment,in order to achieve coverage comparable with that available from thedata channel region resource blocks 415, the control channel region 410for coverage limited UEs is arranged to take up the same amount ofresource space as the resource blocks of the data region 415. In anotherexample, the control channel region 410 for coverage limited UEs may bechannel coded to code the control channel region more strongly than theRBs transmitted in region 415. In this example, channel coding maycomprise turbo coding. Further, in this example RBs 420 may comprise aPDSCH region (not shown).

In this example embodiment, as discussed above, the control processor ofthe eNodeB 210 may be operable to vary the power spectral density oftransmitted RBs, without necessarily increasing the total power appliedto the carrier 425.

If the total power transmitted by the eNodeB in the prior art isP_(tot), then the power per resource block 415 transmitted in the priorart is P_(tot)/N_(RB).

If the same total power is applied by the eNodeB to the transmission inthis invention, then the power per resource block 415 transmitted in theinvention is P_(tot)/ N_(coverage).

The gain in the power transmitted per resource block 415 in theinvention is thus N_(RB)/N_(coverage). For a 20 MHz host system, thepower per resource block 415 may be increased by up to 100/1=>20 dB(noting that a 20 MHz system occupies roughly 100 resource blocks andthe coverage-enhanced system may transmit a single resource block 415).In this example, the eNodeB 210 signals the number of resource blocks415 active in the system in a master information block (MIB). In oneexample, the control processor of the eNodeB 210 may be arranged to onlysignal the number of resource blocks 415, and not the bandwidth beingused. Therefore, the eNodeB may signal via the MIB that the carrier 425comprises a 100 resource block carrier and that in subframes used forcoverage limited UEs, one resource block per subcarrier could beutilised. It is noted that an LTE system can transmit 100 resourceblocks in less than a 20 MHz carrier, for example a 19.5 MHz carriercould be used.

In some examples, it may be possible to utilise a fraction of a resourceblock 415, say a half of a resource block. This example has an advantagethat the power per resource block may be further increased. As discussedpreviously, if N_(coverage) comprises a single RB 415, the transmittedpower in this RB 415 may be increased by upto 20 dB when compared to aprior art system. Utilising a fractional value of a RB 415 allows thetransmitted power to be further increased. In this example, it isenvisaged that a range from 1RB to 0.5RB may be utilised successfully inorder to increase the power per RB 415. In this example, utilising halfan RB would further increase the power per resource block to roughly 23dB, when compared to a prior art 20 MHz system.

In another example embodiment, less than half a RB 415 may be utilisedby the eNodeB. In this case, it may be necessary to utilise a differentreference signal structure as there would need to be an appropriatenumber of reference signals in the fractional resource block.

Separate control channel regionAs discussed above, examples of theinvention may incorporate a separate control channel region 410 for thecoverage limited UEs. This is beneficial since the legacy control region405 is transmitted across the entire system bandwidth and, hence, thepower per subcarrier of the legacy control region 405 cannot beincreased. In contrast the separate control channel region 410 for thecoverage limited UEs may be transmitted in a lower number of resourceblocks 415 (and the power of the resource blocks for thecoverage-limited UEs can be increased).

PDCCH and PDSCH Spanning Multiple Subframes

It may appear that the restricted number of resource blocks available inthe control channel region 410 for the coverage limited UEs may be seenas limiting the number of UEs that can be scheduled, however this is nota serious concern. The aspect of system operation that is important isthe ratio of the amount of physical resource available in the controlchannel region to the amount of resource available in the PDSCH region.In a legacy LTE system, there are three symbols out of a possiblefourteen symbols that may be used for the legacy control region 405. Inthis example embodiment, one of the possible three symbols is requiredfor legacy devices in order to maintain compatibility with Release-10systems, as legacy UEs expect at least one symbol's worth of controlchannel 405 in each subframe. However, the remaining two symbols thatare normally utilised by the legacy control channel 405 may be utilisedby the control channel for coverage limited UEs 410. In some examples,the control channel 410 for coverage limited UEs may require additionalsymbols. In this case, the eNodeB 210 is operable to utilise some of thePDSCH region of the RBs 415 in order to increase the size of the controlchannel 410 for coverage limited UEs.

Therefore, in some example embodiments, the eNodeB 210 is operable todynamically determine size of the control channel region 410 forcoverage limited UEs, for example by using some symbols originallydesignated for the legacy control channel 405 and some symbolsoriginally designated for PDSCH. In one example, the control processorof the eNodeB 210 may be arranged to determine a size of the controlchannel 410 for coverage limited UEs based on the number ofcoverage-limited UEs to be simultaneously scheduled.

One potential issue with the smaller amount of resource available in theseparate control channel region 410, shown in FIG. 4, is that a singleallocation message (e.g. PDCCH) may not fit within the single resourceblock that has been reserved for the control region. This issue may beresolved by allowing PDCCH messages to occupy more than a singlesubframe. In some example embodiments, both PDCCH and PDSCH channels mayoccupy more than a single subframe. Increasing a time duration of thePDCCH (and potentially the PDSCH) may increase the latency of thesystem, however this may not be a concern for some delay tolerant MTCapplications such as smart metering, for example.

FIG. 5 illustrates a simplified example schematic diagram 500 of a PDCCH505 that occupies subframe 1 510 and subframe 2 515 allocating a PDSCH520 occupying subframe 3 525 and subframe 4 530. The PDCCH 505 in thisexample would typically be interleaved across subframe 1 510 andsubframe 2 515. Similarly, the PDSCH 520 would typically be interleavedacross subframe 3 525 and subframe 4 530.

There are several consequences of increasing the duration of the PDCCH505 and PDSCH 520 messages. For example each of the interleaved PDCCH505 and PDSCH 520 messages occupy multiple subframes, thereby increasinglatency in the system as a UE would have to wait for the entire PDCCHmessage interleaved over two subframes and the entire PDSCH messageinterleaved over two subframes in order to correctly decode the message.In another example, PDCCH 505 and PDSCH 520 messages may be interleavedover any number of subframes. In another example, any spare PDCCH 505that is not utilised 525 may be used by a subsequent PDCCH message.Furthermore, any spare PDSCH 520 that is not utilised 530 may be used bya subsequent PDSCH message. The PDCCH 505 and PDSCH 520 are shownoccupying separate sets of subframes. Extending the PDCCH and PDSCHacross multiple subframes can also be applied when PDCCH 505 and PDSCH520 occupy the same subframes (for example PDCCH occupies subframes 510and 515; and PDSCH occupies subframes 510 and 515). In order to decodesuch an arrangement, the UE would have to buffer physical bits from allsubframes occupied by the PDCCH and PDSCH (e.g. subframes 510 and 515)before decoding those buffered physical bits.

In this example embodiment, the eNodeB includes a scheduler 297 locatedwithin the eNodeB 210. In another example embodiment, the scheduler maybe located elsewhere within the network architecture. In this example,the scheduler 297 is operable to make a scheduling decision on the PDSCH520 earlier than in a legacy LTE case, for example due to potentialinterleaving of PDCCH 505. In this manner, the scheduler 297 is arrangedto determine how much PDSCH 520 resource is to be scheduled before thePDCCH 505 is transmitted. If interleaving is utilised, the PDCCH 505 maytake longer to transmit, and hence any scheduling decision will need tobe determined earlier than in a legacy LTE case.

FIG. 6 illustrates a simplified example flow diagram 600 of an eNodeButilising aspects of the invention. Initially, at 602, the eNodeB (suchas eNodeB 210 of FIG. 2) waits for a predetermined number of subframesbefore determining at 604 whether the amount of some broadband LTEtraffic may be less than a threshold value. If it is determined at 604that the amount of some broadband LTE traffic is greater than athreshold value, the eNodeB may send coverage extension beacon andsynchronisation signals sparsely at configured times in 606. By sendingthese signals sparsely, the eNodeB allows coverage limited UEs tosynchronise with the loaded cell, allowing the UEs to indicate to theeNodeB that they have data to send (e.g. via PRACH), but the sparsenature of these signals does not use a significant amount of resource inthe loaded cell. At 608, the eNodeB determines whether it has receivedphysical random access channel (PRACH) requests from coverage limitedUEs. If it has received such requests, the eNodeB operation proceeds to610, otherwise the eNodeB operation returns to 602.

If, at 604, the eNodeB determines that broadband LTE traffic is lessthan a threshold value, the eNodeB reconfigures its system to define aset of subframes as multimedia broadcast single frequency network(MBSFN) subframes or almost blank subframes (ABS) at 610. This is donesince when there is little broadband traffic in the cell, the resourcesmay as well be applied to serving MTC UEs instead. At 612 the eNodeBsignals a reconfiguration message to broadband UEs in the cell. Thereconfiguration includes an indication of the subframes that are beingdeclared as MBSFN subframes. At 614 the eNodeB transmits a full set ofcoverage extension beacon and synchronisation signals and, at 616, mayrequest a path loss measurement form a desired UE. At 618, the eNodeBdetermines power requirements of, say, PDCCH and PDSCH signals based onthe UE path loss measurement from 616.

At 620, the eNodeB configures subframes used for coverage extension touse a defined number of resource blocks consistent with the transmitpower available at the eNodeB. At 622, the eNodeB signals the number ofRBs applied to subframes used for coverage extension to UEs requiringcoverage extension. The eNodeB then, at 624, waits for downlink trafficto a UE or a PRACH request from a coverage limited UE (the UE may sendPRACH to the eNodeB when it has uplink data to transmit, but has notalready been scheduled with uplink resource). The eNodeB then runs ascheduler, at 626, to determine those UEs to schedule in subframes for acoverage extension mode of operation. At 628, the eNodeB begins totransmit PDCCH using the required power level and the number of resourceblocks determined previously, and waits until the end of the PDCCHtransmission at 630. At 632, the eNodeB begins to transmit PDSCH signalsusing the required power level and number of resource blocks determinedpreviously. At 634, after the PDSCH transmission, the eNodeB sets up itsreceiver to decode PUCCH or PUSCH based on the amount of physicalresource applied to the UEs for these uplink channels. At 636, theeNodeB determines whether the usage of coverage extension subframes isgreater than a threshold value. If the eNodeB determines that the usageof coverage extension subframes is greater than the threshold value, theeNodeB returns to 624, otherwise the eNodeB returns to 602. In returningto 602, the cell may be reconfigured to not apply MBSFN subframes forcoverage extension purposes (this aspect is not shown in FIG. 6).

In one example embodiment, a consequence of increasing the duration ofPDCCH 505 and PDSCH 520 is that the hybrid automatic repeat request(HARQ) cycle may need to be extended. In this example, the HARQ cycle isthe time between a scheduling decision being made and an acknowledgement(ACK) or negative acknowledgement (NACK) finally being returned from theUE. Referring back to FIG. 5, in this example embodiment, the HARQcycle, may have to be extended by three subframes, In a legacy LTEsystem, PDSCH processing can begin immediately after the subframe thatcontains the combined PDCCH and PDSCH. However, in this exampleembodiment, PDSCH 520 processing may only commence after the end ofsubframe 4 530.

In another example embodiment, it may be possible to utilise fewer HARQprocesses, since the ratio of the reception time (e.g. the time toperform receiver signal processing functions) to transmission time (forexample, 4 subframes for FIG. 5) may be less when implementing theconcepts herein described. Hence, example embodiments may provide theopportunity to operate with fewer HARQ processes when considering lowcomplexity MTC UEs.

Signalling between eNodeB and UE: As part of legacy LTE operation, a UEmay be required to perform uplink power control and channel estimation.Generally, a UE is able to estimate the path loss between an eNodeB andthe UE in order to control the power of uplink channels. Thismeasurement is usually performed by comparing reference signal receivedpower (RSRP), also known as received power per reference signal, totransmitted power per reference signal. This is signalled to the UE onsystem information block 2 (SIB2). Furthermore, the UE is operable toperform channel estimation using reference signals that are containedwithin the resource blocks that are allocated to the UE. The UE may alsobe able to use reference signals outside those reference blocks, forexample some ‘outside’ reference signals may be used to interpolate thechannel with reference signals that are contained within the resourceblocks, thereby potentially avoiding edge-effects in the estimation ofthe channel by the UE.

In both of the abovementioned cases, the UE may be required to know thephysical resources that are active in the entire system, in addition tothe physical resources that are allocated to itself. Once the UE knowsthe physical resources that are active in the entire system, it is ableto determine those reference signals that are active and can use thosereference signals to determine an overall RSRP. It may also use thosereference signals for interpolation purposes when performing channelestimation.

In this example embodiment, the UE is operable to utilise any activereference signal. Determining which reference signals are active mayprevent the UE from attempting to interpolate to reference signals thatare not present in the system.

In one example embodiment, the control processor and the transceiver ofthe eNodeB may be arranged to signal how much physical resource isactive in each subframe to the UE. In this manner, the UE is able toknow how much physical resource is active in the entire system, as wellas the physical resources allocated to it, and can then determine anoverall RSRP.

In one example embodiment, the control processor and the transceiver ofthe eNodeB may be arranged to transmit a robust signalling sequencewithin every subframe to a UE. Such a robust signalling sequence may bearranged to allow the UE to readily identify the amount of resource thatthe eNodeB is transmitting in total. In this example embodiment, therobust signalling sequence may, for example, be a correlation sequence.In another example embodiment, the robust signalling sequence may be acyclic shift of a known bit sequence.

In one example embodiment, the control processor and the transceiver ofthe eNodeB may be arranged to signal the total amount of physicalresource applied in a cell using a single RB. The robust signallingsequence may also be transmitted in the minimum amount of physicalresource that the eNodeB can use, which in one example may be a singleRB. In this example or another example embodiment, the single RB may beoperable to contain information that indicates that the eNodeB is alsotransmitting further resource blocks. This use of a single RB providesan advantage in that all desired UEs in the system will be able toreceive and decode this information, since it is being transmitted atthe highest power spectral density

In another example embodiment, the robust signalling sequence may bespread over the resource blocks that the eNodeB utilises in any onesubframe. In this example embodiment, the signalling sequence used toindicate that the eNodeB is transmitting ‘N’ resource blocks may bearranged to be orthogonal to the signalling sequence it uses to indicatethat it is transmitting ‘M’ resource blocks.

In another example embodiment, the control processor and the transceiverof the eNodeB may be arranged to signal the total amount of physicalresource applied in a cell using a dynamically determined number of RBs.In this manner, the eNodeB is operable to dynamically select those UEsto signal within the system.

In one example embodiment, the control processor and the transceiver ofthe eNodeB may be arranged to signal subframes using system informationblock signalling.

In a further example embodiment, the control processor and thetransceiver of the eNodeB may be arranged to signal how much physicalresource is active in each subframe to the UE, for example using adefined sequence of subframes (wherein the total amount of physicalresource used in certain subframes within a sequence is defined by theeNodeB). For example, the defined sequence of subframes may beconfigured dependent upon the coverage conditions of the set ofreceiving UEs: the eNodeB may configure the amount of available physicalresource available in different subframes in proportion to the number ofUEs with certain path losses.

In this example embodiment, the control processor and the transceiver ofthe eNodeB may be arranged to, as part of some broadcast signalling,signal to the UE those subframes in which it will transmit using only asingle RB, those in which it will transmit using two RBs, etc.

For example, UEs situated in good coverage locations may be scheduledwith subframes that use, say, two RBs at a medium power level, forexample. This allows the UEs that are not at the extremity of thecommunication coverage capability of the eNodeB to utilise moreresource.

For example, UEs situated in a poor coverage location may be scheduledwith subframes that use, say, a single RB at a high power level, forexample. Alternatively, in yet further example embodiments, UEs inextremely poor coverage conditions, as determined by the eNodeB, may besignalled using fractional values of RBs. In some examples, it isenvisaged that the eNodeB's use of RBs may extend to use of both integervalue(s) and fractional value(s) combined, e.g. 1.5 RBs being used.

In one example, the defined sequence of subframes may comprise almostblank subframes and/or MBSFN subframes.

Alternatively, in another example embodiment, the UE may employ blinddecoding. Here, a UE attempts to decode an eNodeB transmission based onan assumption that the eNodeB is transmitting a single RB. The UE may beoperable to determine a signal-to-interference plus noise ratio (SINR)based on this first assumption. Similarly, the UE may be furtheroperable to decode on an assumption that the eNodeB is transmitting twoRBs. The UE is operable to determine an SINR based on this secondassumption. The UE may then select the assumption with the best measuredSINR and complete the decoding process based on that SINR.

In another example embodiment, the UE may only determine the SINR forassumptions based on its knowledge of channel conditions. For example,in poor channel conditions, the UE may not determine an SINR for a largenumber of RBs, as the UE may assume that, due to poor channelconditions, only a small number of RBs, e.g. a single RB, would be used.

FIG. 7 illustrates a simplified example flowchart 700 of a wirelesscommunication unit, such as a UE, utilising aspects of the presentinvention. In this example, the UE is a coverage limited UE wishing tocommunicate with an eNodeB.

Initially, at 702, the UE waits for a predetermined number of subframes,before determining, at 704, whether an eNodeB is transmitting a coverageextension beacon and synchronization signals. If the UE determines thatthe eNodeB is not transmitting coverage extension beacon andsynchronization signals, it determines, at 706, whether the eNodeB istransmitting sparse beacon and synchronization signals instead. If theUE determines at 706 that the eNodeB is transmitting sparse beacon andsynchronization signals, it sends a physical random access channel(PRACH) signal or a PRACH preamble signal to the eNodeB indicating thatit is coverage limited at 708, before returning to 702.

Otherwise, if the UE determines at 706 that the eNodeB is nottransmitting sparse beacon and synchronization signals, the UE 700searches for a coverage extension signals from another cell at step 710.

If the UE determines that the eNodeB is transmitting coverage extensionbeacon and synchronization signals at 704, the UE connects to thiseNodeB and sends a path loss measurement at 712. The UE then readssystem information provided by the eNodeB, at 714, which may includeinformation on the number of RBs active in the cell and the subframesthat have been configured for operation with coverage extension. The UEis then operable to perform channel estimation based on the configurednumber of RBs in the cell, at 716, before waiting for a subframeboundary on which a PDCCH can begin, at 718. In this example, thewaiting for a subframe boundary relates to the fact that some PDCCH mayneed to be transmitted across a plurality of subframes (as describedwith reference to FIG. 5). In 718, if PDCCHs are transmitted in a singlesubframe, a PDCCH can begin on every subframe boundary that isconfigured for coverage extension operation: noting that only certainsubframes, e.g. MBSFN subframes, may be configured for operation in acoverage extension mode.

The UE is then operable to decode the PDCCH in subframes that areconfigured for coverage extension operation, at 720, before decodingPDSCH in subframes configured for coverage extension operation accordingto PDCCH in 722. The UE is then operable, in 724, to respond to theeNodeB using PUCCH or PUSCH according to the UE's configuration and thedegree to which it is coverage limited. In 726, the UE determineswhether a disconnect signal has been received from the eNodeB, orwhether coverage extension beacon/synchronization signals havedisappeared. If the UE determines that it has not received a disconnectsignal from the eNodeB in 726, or that coverage extensionbeacon/synchronization signals have not disappeared it returns to 718;otherwise it disconnects from the eNodeB at 728.

As discussed above, it may be possible for an eNodeB to transmit lessthan a single RB. FIG. 8 illustrates a legacy single RB 800, comprising12 subcarriers 802, 14 symbols per subcarrier 804, with a number of thesymbols carrying reference signals 806, denoted by solid blocks. In thisexample, RB 800 refers to a 3GPP™ Release-10 RB, where the referencesignals 806 are evenly spread out throughout the RB 800. This figureonly illustrates cell specific reference signals. In one example, wherea fraction of a RB 808 are to be utilized, for example to furtherincrease power spectral density, the position of the reference signals806 are re-arranged, as shown. In this example, RB 808 comprises twothirds of a legacy RB, employing only eight subcarriers 810. Thus, inthis example, RB 808 has been reduced in size, however the position andquantity of the reference signals are maintained as being substantiallycomparable to the 3GPP™ Release-10 RB 800.

In another example embodiment, the RB 808 may be further reduced in sizeby further reducing the number of subcarriers, for example to furtherincrease power spectral density. In this example, a different referencesignal 806 structure may be used to ensure that an appropriate number ofreference signals 806 within the fractional RB are transmitted.

Maintaining the reference signal structure from RB 800 in RB 808 has theadvantage that channel estimation algorithms developed for RB 800 can bereadily modified to the structure of RB 808.

Frequency Hopping

In order to allow for frequency diversity, RBs or sets of resourceelements (REs: where a resource element is a single subcarrier occupyinga single symbol) that are applied to coverage-limited UEs may befrequency hopped on, say, a symbol-by-symbol basis or on, say, asubframe-by-subframe basis. Frequency hopping would increase frequencydiversity and would reduce the impact of inter-cell interference (e.g.adjacent cells serving coverage limited UEs could apply a differenthopping pattern and adjacent cells serving normal UEs would not seeisolated interference in a restricted set of RBs).

When frequency hopping is applied, a reduced number of physical RBs orsets of REs could be used in the cell (as for other aspects of theinvention, as previously described), but the frequency location of thosephysical RBs or sets of REs may change (from symbol-to-symbol or fromsubframe-to-subframe, dependent upon the characteristics of the hoppingpattern).

When a UE is frequency hopped, there may be some switching delayrequired between the hopped frequencies (to allow the UE to retune itsRF circuits for example). Therefore, in one example embodiment, in orderto accommodate this switching delay, a time gap may be inserted betweenthe frequency hops. In this manner, other coverage limited UEs can thenbe time-multiplexed (or interleaved) into these time gaps.

Referring now to FIG. 9, an example simplified schematic drawing 900 ofa frequency hopping scheme that allows plural (in this example, two)slow switching UEs to be time-multiplexed into LTE subframes is shown.The schematic drawing 900 illustrates a number of subframes 902, legacycontrol regions 904, first frequency hopped sets of REs 906 applied to afirst UE (UE_A) and second frequency hopped sets of REs 908 applied to asecond UE (UE_B). In this example embodiment, for coverage limited UEs,a single resource block (or set of REs) applied by an eNodeB may befrequency hopped. Further, two (or more) UEs may be time multiplexed inthe frequency hopping pattern, for example during the time when UE_A isnot assigned resources in the hopping pattern, UE_B may be assignedresources. UE_A may use this ‘spare’ time to retune its RF circuitsbetween different frequencies within the hopping pattern. In thisexample embodiment, the time to retune RF circuits (e.g. switching time)should be reasonable to enable retuning within a single timeslot. Inthis example, a time of 0.5 ms is utilised, however other values areenvisaged, for example in other example embodiments the switching timemay be less than 0.1 ms. In other example embodiments, switching timemay be between two and seven symbols, where a symbol lasts for 0.07 ms (1/14). In this example, FIG. 9 would be time multiplexed between 2 and 8UEs to allow for switching time of the UEs.

Referring now to FIG. 10, a simplified example block diagram of thetransmission of uplink signals on a single subcarrier is illustrated,according to aspects of this invention. The simplified example blockdiagram comprises legacy 3GPP™ Release-10 RB 1000 and coverage limitedRB 1008 in accordance with examples of the invention. Legacy 3GPP™Release-10 RB 1000 further comprises 12 subcarriers 1002, timeslots 1004and uplink reference signals 1006. In some examples, uplink signals maybe power controlled according to the current LTE specifications. At thecell edge, these signals may be sent in a minimum of a single resourceblock. In order to increase the coverage of these uplink signals,according to this invention, they can be transmitted in less physicalresource than a single resource block: down to a single subcarrier. Useof a single subcarrier allows the UE to concentrate its energy into thatsingle subcarrier. In LTE, an uplink physical resource block consists of12 subcarriers. Hence the potential coverage gain from transmissionusing a single subcarrier is 10×log₁₀(12)=10.8 dB.

When a single subcarrier is transmitted in the uplink coverage limitedRB 1008, the other 11 subcarriers of the physical resource block 1110can be assigned to other UEs. This has an advantage that, in the uplink1008, there is not necessarily a spectral efficiency loss associatedwith serving coverage limited UEs. This is in contrast to the case forthe downlink, as in the downlink case, the eNodeB assigns all its powerto the limited number of subcarriers to improve coverage. Those unusedcarriers cannot be reused since the eNodeB does not have sufficientpower to service those unused subcarriers (note that if the power of theeNodeB were increased, these otherwise unused subcarriers could bebrought into operation using the additional power while the coveragelimited UEs could still be served with the baseline eNodeB poweraccording to the techniques described hereinbefore). The uplink case isdifferent. If a UE does not have enough power to transmit a lot ofsubcarriers, a different UE (with its own power source) can transmit onthose other subcarriers.

Note that an uplink signal transmitted on a single subcarrier will beable to transmit fewer bits than an uplink signal transmitted on aminimum of a single physical resource block. In order to combat thislimitation, a similar approach to that used in the downlink can beapplied: the uplink signal can be transmitted across multiple subframes(as described with reference to FIG. 5).

It will be appreciated that, for clarity purposes, the describedembodiments of the invention with reference to different functionalunits and processors may be modified or re-configured with any suitabledistribution of functionality between different functional units orprocessors is possible, without detracting from the invention. Forexample, functionality illustrated to be performed by separateprocessors or controllers may be performed by the same processor orcontroller. Hence, references to specific functional units are only tobe seen as references to suitable means for providing the describedfunctionality, rather than indicative of a strict logical or physicalstructure or organization.

Aspects of the invention may be implemented in any suitable formincluding hardware, software, firmware or any combination of these. Theinvention may optionally be implemented, at least partly, as computersoftware running on one or more data processors and/or digital signalprocessors. For example, the software may reside on non-transitorycomputer program product comprising executable program code to increasecoverage in a wireless communication system. The program code isoperable for, at a network element: transmitting a first portion ofsubframes comprising a number of resource blocks to a first wirelesscommunication unit in a first mode of operation, wherein the number ofresource blocks are transmitted at a first power level per resourceblock; and transmitting, a second portion of subframes to a secondwireless communication unit in a second mode of operation at a secondpower level, wherein the second portion of subframes comprise a lowernumber of resource blocks than the first portion of subframes and thelower number of resource blocks is transmitted at a second power levelper resource block that is higher than the first power level perresource block. The program code is operable for, at a wirelesscommunication unit: receiving in a second extended coverage mode ofoperation, a signal comprising subcarriers transmitted at a second powerlevel, wherein the signal comprises a second portion of subframes;wherein the second portion of subframes comprise a lower number ofresource blocks than a first portion of subframes transmitted at a firstpower level in a first non-extended coverage mode of operation, andwherein the lower number of resource blocks is transmitted at a secondpower level per resource block that is higher than the first power levelper resource block.

Thus, the elements and components of an embodiment of the invention maybe physically, functionally and logically implemented in any suitableway. Indeed, the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units.

Those skilled in the art will recognize that the functional blocksand/or logic elements herein described may be implemented in anintegrated circuit for incorporation into one or more of thecommunication units. Furthermore, it is intended that boundaries betweenlogic blocks are merely illustrative and that alternative embodimentsmay merge logic blocks or circuit elements or impose an alternatecomposition of functionality upon various logic blocks or circuitelements. It is further intended that the architectures depicted hereinare merely exemplary, and that in fact many other architectures can beimplemented that achieve the same functionality. For example, forclarity the control processor 296 and control processor 308 have beenillustrated and described as a single processing module, whereas inother implementations they may comprise separate processing modules orlogic blocks.

Although the present invention has been described in connection withsome example embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the scope of the presentinvention is limited only by the accompanying claims. Additionally,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognize thatvarious features of the described embodiments may be combined inaccordance with the invention. In the claims, the term ‘comprising’ doesnot exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

The invention claimed is:
 1. A method for increasing coverage in awireless communication system, the method comprising, at a networkelement: transmitting a first portion of subframes comprising a numberof resource blocks to a first wireless communication unit in a firstmode of operation, wherein the number of resource blocks are transmittedat a first power level per resource block; transmitting, a secondportion of the subframes to a second wireless communication unit in asecond mode of operation at a second power level, wherein the secondportion of subframes comprise a lower number of resource blocks than thefirst portion of subframes and the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block; scheduling a firstcontrol channel region in the first portion of subframes and schedulinga second separate additional control channel region in the secondportion of subframes.
 2. The method of claim 1 wherein the secondportion of subframes comprises at least one from a group comprising:almost blank subframes, multimedia broadcast single frequency network(MBSFN) subframes.
 3. The method of claim 2 wherein scheduling a secondseparate additional control channel region in the second portion ofsubframes unit comprises scheduling at least one of: a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), a physical control format indicator channel (PCFICH).
 4. Themethod of claim 3 wherein the channels transmitted by the secondadditional separate control channel region occupy more than a singlesubframe.
 5. The method of claim 1 further comprising scheduling thesecond separate additional control channel region in the second portionof subframes is performed across multiple subframes.
 6. The method ofclaim 5 wherein the second separate additional control channel regioncomprises a control channel signal that allocates a shared downlinkresource to the second wireless communication unit.
 7. The method ofclaim 6 wherein at least one of the control channel signal and theshared downlink resource are interleaved over a plurality of secondportion of subframes.
 8. The method of claim 1 wherein the wirelesscommunication system is a long term evolution communication system. 9.The method of claim 1 wherein the lower number of resource blocks usedin the second portion of subframes comprise less than a single physicalresource block.
 10. The method of claim 1 further comprising schedulingthe second portion of subframes in time multiplexed frequency hoppedtransmissions such that multiple wireless communication units aresupported within available downlink resource in a first communicationcell.
 11. The method of claim 10 wherein scheduling the second portionof subframes such that multiple wireless communication units are timemultiplexed within available downlink resource comprises inserting atime gap between frequency hops.
 12. The method of claim 11 wherein aresource block in the frequency hopping comprises a first number ofsymbols and a second number of subcarriers.
 13. The method of claim 1further comprising determining a power requirement of multiple wirelesscommunication units and scheduling a number of resource blocks for thesecond portion of subframes based at least on the determined powerrequirement of the second wireless communication unit.
 14. The method ofclaim 13 wherein determining a power requirement of the second wirelesscommunication unit comprises at least one from a group comprising:requesting a path loss measurement from the second wirelesscommunication unit, receiving channel quality information transmitted bythe second wireless communication unit, receiving an indication from thesecond wireless communication unit of the power that it is using for itstransmissions.
 15. A non-transitory computer program product comprisingexecutable code stored therein for increasing coverage in a wirelesscommunication system, wherein the code is operable for, when executed ata network element, performing the method of claim
 1. 16. A networkelement for increasing coverage in a wireless communication system, thenetwork element comprising a transceiver operably coupled to a controlprocessor, wherein the control processor is arranged to: transmit, afirst portion of subframes comprising a number of resource blocks to afirst wireless communication unit in a first mode of operation, whereinthe number of resource blocks are transmitted at a first power level perresource block; transmit a second portion of subframes to a secondwireless communication unit in a second mode of operation at a secondpower level, wherein the second portion of subframes comprise a lowernumber of resource blocks than the first portion of subframes and thelower number of resource blocks is transmitted at a second power levelper resource block that is higher than the first power level perresource block; scheduling a first control channel region in the firstportion of subframes and scheduling a second separate additional controlchannel region in the second portion of subframes.
 17. An integratedcircuit for a network element for increasing coverage in a wirelesscommunication system, the integrated circuit comprising a controlprocessor, wherein the control processor is arranged to: transmit afirst portion of subframes comprising a number of resource blocks to afirst wireless communication unit in a first mode of operation, whereinthe number of resource blocks are transmitted at a first power level perresource block; transmit a second portion of subframes to a secondwireless communication unit in a second mode of operation at a secondpower level, wherein the second portion of subframes comprise a lowernumber of resource blocks than the first portion of subframes and thelower number of resource blocks is transmitted at a second power levelper resource block that is higher than the first power level perresource block; scheduling a first control channel region in the firstportion of subframes and scheduling a second separate additional controlchannel region in the second portion of subframes.
 18. A method forcommunicating in an increased coverage area in a wireless communicationsystem, the method comprising, at a wireless communication unit:receiving in a second extended coverage mode of operation, a signalcomprising subcarriers transmitted at a second power level, wherein thesignal comprises a second portion of subframes that includes a secondcontrol channel region; wherein the second portion of subframes comprisea lower number of resource blocks than a first portion of subframes thatincludes a first control channel region that is separate from the secondcontrol channel region and that is transmitted at a first power level ina first non-extended coverage mode of operation, and wherein the lowernumber of resource blocks is transmitted at a second power level perresource block that is higher than the first power level per resourceblock.
 19. A non-transitory computer program product comprisingexecutable code stored therein for communicating in an increasedcoverage area in a wireless communication system, wherein the code isoperable for, when executed at a wireless communication unit, performingthe method of claim
 18. 20. A wireless communication unit comprising: areceiver for receiving in a second extended coverage mode of operation,a signal comprising subcarriers transmitted at a second power level,wherein the signal comprises a second portion of subframes; and acontrol processor, operably coupled to the receiver and arranged todecode the signal wherein the second portion of subframes comprise alower number of resource blocks than a first portion of subframestransmitted at a first power level in a first non-extended coverage modeof operation, and wherein the lower number of resource blocks istransmitted at a second power level per resource block that is higherthan the first power level per resource block, and further wherein thefirst portion of subframes includes a first control channel region andthe second portion of subframes includes a second separate additionalcontrol channel region.
 21. An integrated circuit for a wirelesscommunication unit comprising: a control processor arranged to decode asignal received in a second extended coverage mode of operation, whereinthe signal comprises subcarriers transmitted at a second power level andcomprises a second portion of subframes, wherein the second portion ofsubframes comprise a lower number of resource blocks than a firstportion of subframes transmitted at a first power level in a firstnon-extended coverage mode of operation, and wherein the lower number ofresource blocks is transmitted at a second power level per resourceblock that is higher than the first power level per resource block, andfurther wherein the first portion of subframes includes a first controlchannel region and the second portion of subframes includes a secondseparate additional control channel region.